This invention relates to a method of manufacturing solid electrolyte capacitors, and more particulary to a method of forming an anode terminal thereof. The usual method of manufacturing chip-type solid electrolyte capacitors as shown in FIG. 1 is as follows. At first, a sintered anode body 1 of a porous valve-metal such as tantalum having a wire 2 of the same valve-metal is formed. In this respect, this sintered anode body 1 is formed by the steps of molding a powder of valve-metal into a predetermined lump having the embedded wire 2 of the same valve-metal and sintering the lump into the anode body, or by the steps of molding a powder of valve-metal into a lump, sintering the limp into the anode body and welding the wire 2 of the same valve-metal to the anode body 1. Then, Teflon ring 3 is inserted to the wire to its root. Then, valve-metal oxide is formed over the entire surface of the sintered anode body by anodic oxidation, and a solid electrolyte layer 4 such as MnO.sub.2 layer is coated thereover. A cathode conductive layer 5 consisting of a graphite layer, a silver paste layer and a solder layer is formed successively over the solid electrolyte layer 4. Then, an anode terminal 7 of wettable or solderable metal is welded to the wire 2, and a cathode terminal 8 is soldered to the cathode conductive layer 5. Finally, a plastic enclosure 6 is formed. However, in such conventional method, crawling of solid electrolyte material to the anode wire 2 is unavoidable during the formation of the solid electrolyte layer 4. Accordingly, in view of the crawling of the solid electrolyte material and deviation thereof, a gap of at least 1mm is needed between the root of the anode wire 2 and the junction of the anode terminal 7 to the anode wire 2. This gap has been a major obstacle to reduce the size of capacitor, especially of a chip-type capacitor.
It is an object of this invention to provide a method of manufacturing solid electrolyte capacitors which are excellent in volumetric efficiency.
It is another object of this invention to provide a method of manufacturing chip-type solid electrolyte capacitors with a high efficiency.
In the method of the present invention, an anode body of a porous valve-metal is prepared, and a dielectric layer is formed over the entire surface of the anode body by anodic oxidation. Next, a solid electrolyte layer and a predetermined cathode layer composed of; for example, graphite layer and silver paste layer are formed over the surface of the dielectric layer. Then a predetermined portion of the anode body is exposed by selectively removing the solid electrolyte and cathode layers and the dielectric layer in the predetermined portion where an anode terminal is to be provided. Next, the boundary of the exposed portion of the solid electrolyte and cathode layers is covered with insulating resin. And then, an anode terminal is attached to the exposed portion of the anode body, by using a metal or metals or other conductive materials other than of the valve-metal of the anode. A cathode terminal is attached to the cathode layer and encapsulation, is done according to the intended purpose, whereby the solid electrolyte capacitor of the present invention is gained.
The solid electrolyte capacitor according to the present invention is characterized in that the anode terminal is directly attached to the selectively exposed surface of the anode body especially of the porous valve metal by using a conductive material, other than the valve-metal of the anode body, such as silver paste, a solder adhesive to ceramics and a conductive organic polymer.
According to th present invention, the volume or size of the solid eletrolyte capacitor can be decreased to a large extent.